It's what happens when anything new comes out. Like how it became cool to bash Burton's Batman after BB. TAS got attacked when the MTV show came out, but fortunately it got canceled and everyone realized how crappy that show was.
This is a good show and probably will be better than TAS, but that does not make TAS bad. But fanboys love trashing what is old and making love to what is new. Look at how Pierce Brosnan was once called "the best Bond since Connery" and now everyone who enjoyed CR cannot help themselves from calling him a bad actor, a bad Bond and too feminine among other things.
It's the sad way the fan culture works.